Osmundacetone modulates mitochondrial metabolism in non-small cell lung cancer cells by hijacking the glutamine/glutamate/α-KG metabolic axis.

BACKGROUND: Osmundacetone (OSC) is a bioactive phenolic compound isolated from Phellinus igniarius and that was shown to exert cytotoxic effects on cancer cells in our previous work. The antiproliferative impact of OSC on non-small cell lung cancer (NSCLC) and the underlying mechanisms, however, have not been studied. PURPOSE: This study aimed to explore the antiproliferative effect of OSC on NSCLC cells and the mechanisms involved. METHODS: Cell viability, colony formation and cell cycle distribution were measured following exposure to OSC in vitro. The anticancer activity of OSC was also examined using a xenograft growth assay in vivo. Furthermore, serum metabolomics analysis by GC-MS was done to detect alterations in the metabolic profile. Next, expression of GLS1 and GLUD1, the key enzymes in glutamine metabolism, was evaluated using RT-PCR and western blot. α-KG and NADH metabolites were assessed by ELISA. Mitochondrial functions and morphology were evaluated using the JC-1 probe and transmission electron microscopy, respectively. The ATP production rate in mitochondria of cells with OSC treatment was determined using a Seahorse XFe24 Analyzer. RESULTS: OSC selectively reduced the proliferation of A549 and H460 cells. OSC triggered G2/M cell cycle arrest and decreased the cell clone formation. A mouse xenograft model revealed that OSC inhibited tumor growth in vivo. Findings of serum metabolomics analyses indicated that the anticancer function of OSC was related to disorders of glutamine metabolism. Such a speculation was further verified by the expression level of GLUD1, which was downregulated by OSC treatment. Concentrations of the related metabolites α-KG and NADH were reduced in response to OSC treatment. Moreover, OSC led to disorganization of the mitochondrial ultrastructure and a decrease in mitochondrial membrane potential. OSC also decreased ATP production via oxidative phosphorylation (OXPHOS) but did not affect glycolysis in NSCLC cells. CONCLUSION: The key role of OSC in mitochondrial energy metabolism in NSCLC cells is to suppress tumor development and cell proliferation downregulating GLUD1 to inhibit the glutamine/glutamate/α-KG metabolic axis and OXPHOS. It indicats that OSC might be a potential natural agent for personalized medicine and an anticancer metabolic modulator in NSCLC chemotherapy.